Graphite to Graphene: Green Synthesis Using Opuntia ficus-indica

Abstract

Green synthesis promotes partial or total substitution of chemicals that are potentially harmful to the environment with more friendly ones and is also concerned with decreasing energy consumption. In this study, commercial graphite (1.0 g) was mixed with Opuntia ficus-indica (Ofi) (1.0 ml) and 50 ml deionized water in a glass beaker. The mixture was sonicated in an ultrasonic bath for 30 min at room temperature. Subsequently, the supernatant was transferred to a glass substrate and dried. To characterize the graphitic nanostructure, we used Raman spectroscopy, x-ray diffraction (XRD) analysis, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Raman spectroscopy was used to characterize the crystal structure. The ratio of the relative intensity of the G and 2D peaks in the Raman spectrum followed by deconvolution of the 2D band suggested that four and five layers of graphene were formed. The XRD profile showed a strong decrease in the (002) peak intensity with a thickness of 0.34 nm characterizing the graphite structure. The C:O ratio measured by XPS showed a degree of oxidation comparable to reports on few-layer graphene (FLG), and AFM images showing the roughness of the sheets revealed small steps of 1 nm with length of about 100 nm. Structural and morphological properties were analyzed by TEM. We found thin graphene layers of about one micron in extent; at 10-nm scale, structures of two, three, four, and five layers were identified. These results suggest that this method can be used for synthesis of FLG via an environmentally friendly route without use of acids or strong chemical oxidants.